Once an anti-Semitic rumor moved from fringe to the mainstream, it took less than two weeks for violence to erupt. The false allegation that liberal philanthropist George Soros was funding or supporting a caravan of Honduran refugees heading to the U.S. spread wildly from a single tweet posted on Oct. 14.

Along withfar-right memes, that allegation helped motivate both an allegedmail-bomber and a massshooter at a Pittsburgh synagogue. The way these messages traveled across the internet in this short time span is just one example of how extremist messages and memes circulate with incredible speed across mainstream social media platforms.

From our vantage point as researchers of visual and digital communication, memes – short, often image-based forms of communication – are powerful engines of persuasion, even though they can appear innocuous or even humorous. Perhaps the best known examples are LOLCats memes, pairing funny pictures of cats with customizable phrases or sentences. Memes can disseminate information quickly because they invite people to share or remix content with little effort required, making widespread dispersal more likely.

Memes need not be humorous or factual to be functional. All they need to do is attract attention online, which often translates into mainstream media coverage. That makes memes potent tools for distributing disinformation. Moreover, the online and mainstream platforms that amplify memes’ circulation can weaponize false claims and encourage conspiracy theorists – sometimes toward violence.

Memes move conspiracies

Understanding how these messages embolden anti-Semitism and other forms of terrorism involves grappling with how white supremacists use digital media. As we detail in our forthcoming book “Make America Meme Again,” messages and memes weaponized in far-right networks are deft political toolsthat move swiftly across social and traditional media. Because memes are stealthy political messages that usually offer rebellious or irreverent humor, they can be easily retweeted, shared or even pasted to the side of a van.

Before the dawn of today’s social media network, right-wing extremists were more difficult to find, often gathering in local communities and later discreetly in online forums unknown to the vast majority of internet users. Paranoid, rabid discourses of this ilk still boil around those darker corners of the internet. Today, memes help right-wing extremists communicate with one another and with mainstream audiences.

The alleged mail bomber covered his van with “images and slogans often found on fringe right-wing social media accounts.” But the suspect didn’t find them on radical sites where white supremacists hide. Instead, based on his social media activity, he likely was radicalized in the same place most people look at cute photos of friends’ kids and check up on Aunt Beatrice – Facebook.

By October, discussions of the “caravan of immigrants” had grown beyond social media. Within a week of that Oct. 14 tweet alleging Soros was funding a group of refugees seeking asylum, far-right commentator Alex Jones broadcast the conspiracy on Infowars, to his audience of over 1 million daily visitors.

The two men may never have known of each other or the other’s plans. But their actions intertwined with a viciously networked conspiracy theory.

Connecting to mainstream media

Once there is enough social media attention on a topic or claim, it may be covered in more traditional news outlets. That can spread the idea even more widely, and lend credence to inaccuracies and lies. Politicians may also notice online discussion and join in, as U.S. Sen. Ted Cruz and a clerk for Texas’ Harris County did with the purported Soros connection to the migrant caravan.

Conspiratorial ideas often become an echo chamber, in which each post draws more attention than the last, generating stronger outrage and escalating the conspiracy. The average user who looks at a conspiratorial meme may not believe its message, but many users may. Even people who don’t believe it initially might come to assume it’s true after seeing an idea several times from different sources. Still others might spread the conspiracy just for amusement in the distress of others.

Demonize, divide, conquer

Memes, tweets and other forms of propaganda are designed to rile up constituents. Scaring voters with purported invasions was one way to infuriate voters as they headed to vote in the midterm elections.

When anti-Semitic, racist and xenophobic ideas spread through social media networks, they can infect a host of mainstream information sources – and make fear and violence more likely. That broadens the picture of a dangerous world from which people need protection. Fear appeals of this sort can influence voting, and even push people to take matters into their own violent hands. Until social media platforms or federal agencies find ways to diminish extremism, the proliferation of far-right memes, videos and texts will continue to imperil the citizenry.